1. Field of the Invention
Method of and equipment for forming an underground fluid-impervious wall by the setting of a liquid material introduced into a vibratorily formed space.
2. Description of the Prior Art
U.S. Pat. No. 3,245,222 discloses a process for constructing an underground dam wherein a trench is formed in soil by hammering a group of aligned elongated solid web members into and, thereafter, successively withdrawing the members, one by one, from the soil while concurrently forcing into the space vacated by the withdrawal of member after member, and as the web members are withdrawn, a liquid grout which sets in the space to form a wall. This method, although widely used, was subject to the drawback that hammering of the web members into the ground caused the soil on both sides of the space thus formed to be compacted. This inhibited penetration of the grout transversely into the soil and resulted in the formation of an underground wall the thickness of which was little, if any, more than the thickness of the web members. Moreover, because the web members were hammered into the ground, there was a tendency to hammer them to the same depth so that their bottoms did not follow the shape of the underlying liquid-impervious layer unless that layer was solid rock; the impacting force was so great that they could be and were driven into and even through underlying liquid-impervious substrates.
In another process, a group of such web members were, for the same purpose, vibratorily driven into the ground and, thereafter, successively vibratorily extracted one after another while liquid grout was introduced into the space being vacated, but the vibrations were not of a frequency such as to encourage an appreciable loosening of the soil structure, so that walls formed heretofore by vibratory driving and extraction were not much thicker than the thickness of the wall members themselves. Moreover in such earlier process no liquid grout was injected under the lower edge of the web members to penetrate the soil during sinking.